clocksource: tcb_clksrc: Make tc_mode interrupt safe

tc_mode() can be called from interrupt context and thus must not call
clk_*prepare*() functions.

Signed-off-by: David Jander <david@protonic.nl>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
ARM: at91: fix at91_sysirq_mask_rtc for sam9x5 SoCs

sam9x5 SoCs have the following errata:
"RTC: Interrupt Mask Register cannot be used
 Interrupt Mask Register read always returns 0."

Hence we should not rely on what IMR claims about already masked IRQs
and just disable all IRQs.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: <stable@vger.kernel.org> # v3.10+
Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Merge branch 'at91-3.15-trunk/v3.15_fixes' into linux-3.15-at91_preview